I3E: A Novel Call Admission Control Scheme for W-CDMA Systems

Efficient Call Admission Control (CAC) techniques are of paramount importance to achieve a flexible radio resource utilization with W-CDMA systems like UMTS. In order to accept or reject a call, the CAC scheme should be able to estimate if the system can provide a Signal-to-Interference Ratio (SIR) high enough to the new call and to all the others. With symmetric traffic the more critical direction for the system capacity is the uplink and the CAC can consider this direction only. Received-Power based CAC (RP-CAC) are practical CAC schemes proposed for the uplink that estimate the system load measuring the total power received at the base stations (BSs). Simple RP-CAC schemes just compare the measured power at the BS where the call is initiated with a threshold (Single Cell RP-CAC) or also measure the power received by neighboring BSs (Multi Cell RP-CAC). More complex RP-CAC schemes try also to estimate the load increase due to the new call (Predictive RP-CAC). In this paper we compare the performance of these schemes and propose a new Predictive scheme, named Iterative Interference Increase Estimation (I3E). We show that the advantage of using multi-cell strategy with respect to the single-cell one is negligible and that previously proposed Predictive RP-CAC techniques are not able to improve the performance in a remarkable way. On the contrary, I3E CAC increases the accepted traffic while keeping the call dropping probability very low, and its performance approaches the upper bound obtained considering an ideal CAC.